The present invention relates to an apparatus for detecting a tunnel. More specifically, the apparatus relates to a photosensor for a vehicle for detecting a tunnel.
Many vehicles include light sensors that actuate various systems of a vehicle based upon ambient light conditions. For example, some sensors provide a signal that changes state as a result of the general level of ambient light. A controller receiving this signal actuates the headlights on when the light level is low and off when the light level is high. However, these sensors necessarily include sufficient filtering of the photosensor electrical signal and/or the response of the controller so as to not be sensitive to brief disturbances in ambient light, such as shadows. Further, these sensors often include a rather wide field of view and include light from ahead, behind, to either side, and from above the vehicle.
Yet another driving situation in which consumers find it desirable to actuate the headlights is the situation presented by the vehicle approaching, within, and exiting a tunnel. Many drivers prefer to have their lights on when inside the tunnel and then turn the lights off as the tunnel is exited. Conventional ambient light sensors have difficulty responding to tunnels. The broad collection of light by such conventional sensors makes them unresponsive to the tunnel until after the tunnel has been entered. Further, those sensors incorporating low pass filtering or other time delays do not turn the headlights on until after the vehicle is well within the tunnel.
What is needed is a tunnel sensor that overcomes the disadvantages of conventional sensors. The present invention does this in a novel and unobvious way.